The vote & record of decision in WFTDA at the end of last year shows that although we were given the option to vote on the chance to restrict numbers to a maximum of 3 for a charter skaters, the membership didn't deem this important - so in that numbers rules change, 4 was allowed to remain an option. This was the vote result:
Do you approve a maximum of three characters instead of four?
Just sharing my ROD knowledge...
Rules of Derby (according to WFTDA) ask our all-knowing officials whatever you like.